This disclosure relates to complementary metal-oxide-semiconductor (CMOS) image sensors. A CMOS image sensor is a type of active pixel sensor made using the CMOS semiconductor process. Extra circuitry next to the sensor such as a readout circuit of the CMOS image sensor converts the light energy received to a voltage signal. Additional circuitry on the imaging sensor such as an analog-to-digital convertor (ADC) may be included to convert the voltage signal to digital data.
During the design of the CMOS image sensor, noise of the image sensor can be simulated either via time domain noise simulation or frequency domain noise simulation. The time domain noise simulation is the analysis of mathematical functions, physical signals or time series data of noise of the image sensor with respect to time. The frequency domain noise simulation refers to the analysis of mathematical functions of noise signals with respect to frequency, rather than time. The time-domain noise simulation shows how the noise of the image sensor changes over time, whereas the frequency-domain noise simulation shows how much of the noise lies within each given frequency band over a range of frequencies.
Some noise sources in the CMOS image sensor may be correlated since these noise sources come from sampling of the same data at different point in time.